Lithium ion battery

ABSTRACT

One embodiment may include a lithium ion battery, wherein one or more chelating agents may be attached to a battery component.

This application claims the benefit of U.S. Provisional Application Ser.No. 61/388,867 filed Oct. 1, 2010.

TECHNICAL FIELD

The technical field relates generally to lithium ion batteries andmethods of making and using the same.

BACKGROUND

Secondary, or rechargeable, lithium ion batteries are well known andoften used in many stationary and portable devices such as thoseencountered in the consumer electronic, automobile, and aerospaceindustries. The lithium ion class of batteries have gained popularityfor various reasons including, but not limited to, a relatively highenergy density, a general nonappearance of any memory effect whencompared to other kinds of rechargeable batteries, a relatively lowinternal resistance, and a low self-discharge rate when not in use.

A lithium ion battery generally operates by reversibly passing lithiumions between a negative electrode (sometimes called the anode) and apositive electrode (sometimes called the cathode). The negative andpositive electrodes are situated on opposite sides of a microporouspolymer separator that is soaked with an electrolyte solution suitablefor conducting lithium ions. Each of the negative and positiveelectrodes is also accommodated by a current collector. The currentcollectors associated with the two electrodes are connected by aninterruptible external circuit that allows an electric current to passbetween the electrodes to electrically balance the related migration oflithium ions. The materials used to produce these various components ofa lithium ion battery are quite extensive. But in general, the negativeelectrode typically includes a lithium intercalation host material, thepositive electrode typically includes a lithium-based active materialthat can store lithium metal at a lower energy state than theintercalation host material of the negative electrode, and theelectrolyte solution typically contains a lithium salt dissolved in anon-aqueous solvent.

A lithium ion battery, or a plurality of lithium ion batteries that areconnected in series or in parallel, can be utilized to reversibly supplypower to an associated load device. A brief discussion of a single powercycle beginning with battery discharge can be insightful on this point.

To begin, during discharge, the negative electrode of a lithium ionbattery contains a high concentration of intercalated lithium while thepositive electrode is relatively depleted. The establishment of a closedexternal circuit between the negative and positive electrodes under suchcircumstances causes the extraction of intercalated lithium from thenegative anode. The extracted lithium is then split into lithium ionsand electrons. The lithium ions are carried through the micropores ofthe interjacent polymer separator from the negative electrode to thepositive electrode by the ionically conductive electrolyte solutionwhile, at the same time, the electrons are transmitted through theexternal circuit from the negative electrode to the positive electrode(with the help of the current collectors) to balance the overallelectrochemical cell. This flow of electrons through the externalcircuit can be harnessed and fed to a load device until the level ofintercalated lithium in the negative electrode falls below a workablelevel or the need for power ceases.

The lithium ion battery may be recharged after a partial or fulldischarge of its available capacity. To charge or re-power the lithiumion battery, an external power source is connected to the positive andthe negative electrodes to drive the reverse of battery dischargeelectrochemical reactions. That is, during charging, the external powersource extracts the intercalated lithium present in the positiveelectrode to produce lithium ions and electrons. The lithium ions arecarried back through the separator by the electrolyte solution and theelectrons are driven back through the external circuit, both towards thenegative electrode. The lithium ions and electrons are ultimatelyreunited at the negative electrode thus replenishing it withintercalated lithium for future battery discharge.

The ability of lithium ion batteries to undergo such repeated powercycling over their useful lifetimes makes them an attractive anddependable power source. But lithium ion battery technology isconstantly in need of innovative developments and contributions that canhelp advance to this and other related fields of technological art.

SUMMARY OF EXEMPLARY EMBODIMENTS

One embodiment may include a lithium ion battery component to whichchelating agents may be attached. The one or more chelating agents cancomplex with metal cations but do not strongly complex with lithium ionsso that the movement of lithium ions in the battery during operation ofthe lithium ion battery is not substantially affected.

Another embodiment may include a lithium ion battery that may comprise anegative electrode, a positive electrode, and a microporous separatorsituated between the negative electrode and the positive electrode. Themicroporous separator may include a polymeric or ceramic material. Thenegative electrode may comprise a lithium host material and a polymerbinder material and/or a ceramic material. The positive electrode maycomprise a lithium-based active material and a polymer binder materialand/or a ceramic material. One or more chelating agents may be attachedto the polymer material and/or ceramic of at least one of themicroporous polymer separator, or other battery component of thenegative electrode, of the positive electrode or other batterycomponent. The one or more chelating agents can complex with metalcations but do not strongly complex with lithium ions so that themovement of lithium ions in the battery is not substantially affected.

Yet another embodiment may include a lithium ion battery that maycomprise a negative electrode, a positive electrode, an interruptibleexternal circuit that connects the negative electrode and the positiveelectrode, a microporous separator to which one or more chelating agentsare attached situated between the negative electrode and the positiveelectrode, and an electrolyte solution capable of conducting lithiumions soaked into the negative electrode, the positive electrode, and themicroporous separator. The microporous separator may comprise at leastone of polyethylene or polypropylene and have pendent groups orinsoluble polymer bound groups that comprise the chelating agents orceramic material having chelating agent bound or attached thereto. Thechelating agents can complex with metal cations that leach from thepositive electrode. The chelating agents, moreover, may comprise atleast one of a crown ether, a podand, a lariat ether, a calixarene, acalixcrown, or a mixture of two or more of these chelating agents.

Other illustrative embodiments of the invention will become apparentfrom the detailed description provided hereinafter. It should beunderstood that the detailed description and specific examples, whiledisclosing illustrative embodiments of the invention, are intended forpurposes of illustration only and are not intended to limit the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Illustrative embodiments of the invention will become more fullyunderstood from the detailed description and the accompanying drawings,wherein:

The FIGURE provided is a schematic and illustrative view of a lithiumion battery, during discharge, according to various embodiments of theinvention. The separator is shown here to help illustrate the flow ofions between the negative and positive electrodes and, as such, is notnecessarily drawn to scale.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The following description of the embodiment(s) is merely illustrative innature and is not intended to limit the invention, its application, oruses.

One embodiment may include a lithium battery component having one ormore chelating agents bound or attached thereto to complex with metalions or trap metal ions. The chelating agents may be bound to polymermaterials, ceramic material or other material of which the batterycomponent comprises. The battery component may include at least one ofthe battery positive electrode, negative electrode, microporousseparator, or other component placed in the battery compartment of whichmake up the battery structure.

A lithium ion battery can suffer cumulative capacity reductions andother detrimental effects, such as the reduction of solvent molecules,when destructive metal cations are introduced into its variouscomponents. To help address such an issue, an appropriate amount of oneor more chelating agents may be attached to the microporous polymerseparator situated between the negative and positive electrodes and/orto the polymer binder material used to construct the negative electrode,the positive electrode, or both. The chelating agents can be chosen toselectively complex with unwanted metal cations that may become presentin the electrolyte solution over the life of the battery. For example,in one embodiment, the immobilization of certain metal cations that maydissolve into the electrolyte solution from the positive electrode(i.e., cations of manganese, cobalt, and/or iron) can help protect thelithium ion battery against negative electrode poisoning and a resultantreduction to its capacity and useful life. The chelating agents thusoperate as metal cation scavenger molecules that trap and immobilizeunwanted metal cations so as to prevent the migration of those metalcations through the electrolyte solution. But at the same time thechelating agents do not strongly complex with lithium ions and, as such,will not adversely affect the movement of lithium ions between thenegative and positive electrodes to the point where an uncharacteristicreduction of the expected electrical current to be supplied by thebattery occurs during discharge.

The FIGURE is a schematic illustration of one embodiment of a secondarylithium ion battery 10 that includes a negative electrode 12, a positiveelectrode 14, a microporous separator 16 sandwiched between the twoelectrodes 12, 14, and an interruptible external circuit 18 thatconnects the negative electrode 12 and the positive electrode 14. Eachof the negative electrode 12, the positive electrode 14, and themicroporous separator 16 may be soaked in an electrolyte solutioncapable of conducting lithium ions. The microporous separator 16, whichoperates as both an electrical insulator and a mechanical support, issandwiched between the negative electrode 12 and the positive electrode14 to prevent physical contact between the two electrodes 12, 14 and theoccurrence of a short circuit. The microporous separator 16, in additionto providing a physical barrier between the two electrodes 12, 14, mayalso provide a minimal resistance to the internal passage of lithiumions (and related anions) to help ensure the lithium ion battery 10functions properly. A negative-side current collector 12 a and apositive-side current collector 14 a may be positioned at or near thenegative electrode 12 and the positive electrode 14, respectively, tocollect and move free electrons to and from the external circuit 18.

The lithium ion battery 10 may support a load device 22 that can beoperatively connected to the external circuit 18. The load device 22 maybe powered fully or partially by the electric current passing throughthe external circuit 18 when the lithium ion battery 10 is discharging.While the load device 22 may be any electrically-powered device, a fewspecific examples of a power-consuming load device include an electricmotor for a hybrid vehicle or an all-electrical vehicle, a laptopcomputer, a cellular phone, and a cordless power tool, to name but afew. The load device 22 may also, however, be a power-generatingapparatus that charges the lithium ion battery 10 for purposes ofstoring energy. For instance, the tendency of windmills and solar paneldisplays to variably and/or intermittently generate electricity oftenresults in a need to store surplus energy for later use.

The lithium ion battery 10 can include a wide range of other componentsthat, while not depicted here, are nonetheless known to skilledartisans. For instance, the lithium ion battery 10 may include a casing,gaskets, terminal caps, and any other desirable components or materialsthat may be situated between or around the negative electrode 12, thepositive electrode 12, and/or the microporous separator 16 forperformance-related or other practical purposes. Moreover, the size andshape of the lithium ion battery 10 may vary depending on the particularapplication for which it is designed. Battery-powered automobiles andhand-held consumer electronic devices, for example, are two instanceswhere the lithium ion battery 10 would most likely be designed todifferent size, capacity, and power-output specifications. The lithiumion battery 10 may also be serially or parallelly connected with othersimilar lithium ion batteries to produce a greater voltage output andpower density if the load device 22 so requires.

The lithium ion battery 10 can generate a useful electric current duringbattery discharge by way of reversible electrochemical reactions thatoccur when the external circuit 18 is closed to connect the negativeelectrode 12 and the positive electrode 14 at a time when the negativeelectrode 12 contains a sufficiently higher relative quantity ofintercalated lithium. The chemical potential difference between thepositive electrode 14 and the negative electrode 12—approximately 3.7 to4.2 volts depending on the exact chemical make-up of the electrodes 12,14—drives electrons produced by the oxidation of intercalated lithium atthe negative electrode 12 through the external circuit 18 towards thepositive electrode 14. Lithium ions, which are also produced at thenegative electrode, are concurrently carried by the electrolyte solutionthrough the microporous separator 16 and towards the positive electrode14. The electrons flowing through the external circuit 18 and thelithium ions migrating across the microporous separator 16 in theelectrolyte solution eventually reconcile and form intercalated lithiumat the positive electrode 14. The electric current passing through theexternal circuit 18 can be harnessed and directed through the loaddevice 22 until the intercalated lithium in the negative electrode 12 isdepleted and the capacity of the lithium ion battery 10 is diminished.

The lithium ion battery 10 can be charged or re-powered at any time byapplying an external power source to the lithium ion battery 10 toreverse the electrochemical reactions that occur during batterydischarge. The connection of an external power source to the lithium ionbattery 10 compels the otherwise non-spontaneous oxidation ofintercalated lithium at the positive electrode 14 to produce electronsand lithium ions. The electrons, which flow back towards the negativeelectrode 12 through the external circuit 18, and the lithium ions,which are carried by the electrolyte across the microporous polymerseparator 16 back towards the negative electrode 12, reunite at thenegative electrode 12 and replenish it with intercalated lithium forconsumption during the next battery discharge cycle. The external powersource that may be used to charge the lithium ion battery 10 may varydepending on the size, construction, and particular end-use of thelithium ion battery 10. Some notable and exemplary external powersources include, but are not limited to, an AC wall outlet and a motorvehicle alternator.

The negative electrode 12 may include any lithium host material that cansufficiently undergo lithium intercalation and deintercalation whilefunctioning as the negative terminal of the lithium ion battery 10. Thenegative electrode 12 may also include a polymer binder material tostructurally hold the lithium host material together. For example, inone embodiment, the negative electrode 12 may be formed from graphiteintermingled in at least one of polyvinyldiene fluoride (PVdF), anethylene propylene diene monomer (EPDM) rubber, or carboxymethoxylcellulose (CMC). Graphite is widely utilized to form the negativeelectrode because it exhibits favorable lithium intercalation anddeintercalation characteristics, is relatively non-reactive, and canstore lithium in quantities that produce a relatively high energydensity. Commercial forms of graphite that may be used to fabricate thenegative electrode 12 are available from, for example, Timcal Graphite &Carbon, headquartered in Bodio, Switzerland, Lonza Group, headquarteredin Basel, Switzerland, or Superior Graphite, headquartered in Chicago,USA. Other materials can also be used to form the negative electrodeincluding, for example, lithium titanate. The negative-side currentcollector 12 a may be formed from copper or any other appropriateelectrically conductive material known to skilled artisans.

The positive electrode 14 may be formed from any lithium-based activematerial that can sufficiently undergo lithium intercalation anddeintercalation while functioning as the positive terminal of thelithium ion battery 10. The positive electrode 14 may also include apolymer binder material to structurally hold the lithium-based activematerial together. One common class of known materials that can be usedto form the positive electrode 14 is layered lithium transitional metaloxides. For example, in various embodiments, the positive electrode 14may comprise at least one of spinel lithium manganese oxide (LiMn₂O₄),lithium cobalt oxide (LiCoO₂), a nickel-manganese-cobalt oxide[Li(Ni_(x)Mn_(y)Co_(z))O₂], or a lithium iron polyanion oxide such aslithium iron phosphate (LiFePO₄) or lithium iron fluorophosphate(Li₂FePO₄F) intermingled in at least one of polyvinyldiene fluoride(PVdF), an ethylene propylene diene monomer (EPDM) rubber, orcarboxymethoxyl cellulose (CMC). Other lithium-based active materialsmay also be utilized besides those just mentioned. Those alternativematerials include, but are not limited to, lithium nickel oxide(LiNiO₂), lithium aluminum manganese oxide (Li_(x)Al_(y)MnO_(1-y)O₂),and lithium vanadium oxide (LiV₂O₅), to name but a few. Thepositive-side current collector 14 a may be formed from aluminum or anyother appropriate electrically conductive material known to skilledartisans.

Any appropriate electrolyte solution that can conduct lithium ionsbetween the negative electrode 12 and the positive electrode 14 may beused in the lithium ion battery 10. In one embodiment, the electrolytesolution may be a non-aqueous liquid electrolyte solution that includesa lithium salt dissolved in an organic solvent or a mixture of organicsolvents. Skilled artisans are aware of the many non-aqueous liquidelectrolyte solutions that may be employed in the lithium ion battery 10as well as how to manufacture or commercially acquire them. Anon-limiting list of lithium salts that may be dissolved in an organicsolvent to form the non-aqueous liquid electrolyte solution includeLiClO₄, LiAlCl₄, LiI, LiBr, LiSCN, LiBF₄, LiB(C₆H₅)₄LiAsF₆, LiCF₃SO₃,LiN(CF₃SO₂)₂, LiPF₆, and mixtures thereof. These and other similarlithium salts may be dissolved in a variety of organic solvents such as,but not limited to, cyclic carbonates (ethylene carbonate, propylenecarbonate, butylene carbonate), acyclic carbonates (dimethyl carbonate,diethyl carbonate, ethylmethylcarbonate), aliphatic carboxylic esters(methyl formate, methyl acetate, methyl propionate), γ-lactones(γ-butyrolactone, γ-valerolactone), chain structure ethers(1,2-dimethoxyethane, 1-2-diethoxyethane, ethoxymethoxyethane), cyclicethers (tetrahydrofuran, 2-methyltetrahydrofuran), and mixtures thereof.

The microporous separator 16 may comprise, in one embodiment, apolyolefin. The polyolefin may be a homopolymer (derived from a singlemonomer constituent) or a heteropolymer (derived from more than onemonomer constituent), either linear or branched. If a heteropolymerderived from two monomer constituents is employed, the polyolefin mayassume any copolymer chain arrangement including those of a blockcopolymer or a random copolymer. The same holds true if the polyolefinis a heteropolymer derived from more than two monomer constituents. Inone embodiment, the polyolefin may be polyethylene (PE), polypropylene(PP), or a blend of PE and PP.

The microporous separator 16 may be a single layer or a multi-layerlaminate fabricated from either a dry or wet process. For example, inone embodiment, a single layer of the polyolefin may constitute theentirety of the microporous separator 16. As another example, however,multiple discrete layers of similar or dissimilar polyolefins may beassembled into the microporous separator 16. The microporous separator16 may also comprise other polymers in addition to the polyolefin suchas, but not limited to, polyethylene terephthalate (PET),polyvinyliderie fluoride (PVdF), and or a polyamide (Nylon). Thepolyolefin layer, and any other optional polymer layers, may further beincluded in the microporous polymer separator 16 as a fibrous layer tohelp provide the microporous polymer separator 16 with appropriatestructural and porosity characteristics. Skilled artisans willundoubtedly know and understand the many available polymers andcommercial products from which the microporous polymer separator 16 maybe fabricated, as well as the many manufacturing methods that may beemployed to produce the microporous polymer separator 16. A morecomplete discussion of single and multi-layer lithium ion batteryseparators, and the dry and wet processes that may be used to make them,can be found in P. Arora and Z. Zhang, “Battery Separators,” Chem. Rev.,104, 4424-4427 (2004).

The chelating agents, which may be attached to the microporous separator16 and/or at least one of the negative electrode 12 or the positiveelectrodes 14, or other battery component and may be any of a variety ofmolecules that can complex with unwanted metal cations to form stableand neutral compounds while, at the same time, not adversely affectingthe flow of lithium ions between the negative and positive electrodes12, 14. The particular chelating agent or agents may, in some instances,be chosen to selectively complex with certain metal cations that areknown or expected to be present in the electrolyte solution at somepoint during operational lifetime of the lithium ion battery 10. Forexample, spinel lithium manganese oxide (LiMn₂O₄) that may be present inthe positive electrode 14 may leach Mn²⁺ cations into the electrolytesolution during normal operation of the lithium ion battery 10. Thesemobile Mn²⁺ cations, in turn, can migrate through the electrolytesolution and across the microporous separator 16 until they eventuallyreach the negative electrode 12. Moreover, if the negative electrode 12is formed from graphite, the Mn²⁺ cations that reach the negativeelectrode 12 tend to undergo a reduction reaction and deposit on thegraphite surface since the standard redox potential of Mn/Mn(II) is muchhigher than that of lithium intercalation into graphite. The depositionof manganese onto graphite in the negative electrode 12 catalyzes thereduction of solvent molecules at the contaminated interface of thenegative electrode 12 and the electrolyte solution causing the evolutionof gases. The poisoned portion of the negative electrode 12 isessentially deactivated and no longer able to facilitate the reversiblegain and loss of intercalated lithium. Similarly, the dissolution ofcobalt cations (Co²⁺) and iron cations (Fe²⁺) from lithium cobalt oxide(LiCoO₂) and lithium iron phosphate (LiFePO₄), respectively, that may bepresent in the positive electrode 14 can also cause capacity losses inthe lithium ion battery 10 by the same or related mechanism. Theleaching of Co²⁺ cations may occur, in one instance, because of anancillary chemical reaction with various adhesives normally used in thepackaging of the lithium ion battery 10. The leaching of Fe²⁺ cationsmay occur, in one instance, because of the presence of hydrofluoric acidthat may be produced through the ingress and egress of water into theelectrolyte solution.

But regardless of the lithium-based active material(s) used in thepositive electrode 14, the leaching rate of metal cations into theelectrolyte solution may vary. The leaching rate of metal cations frompositive electrode 14 may be relatively slow and require several yearsfor the electrolyte solution to accumulate a concentration of associatedmetal cations measurable in parts per million (ppm). The leaching rateof metal cations from the positive electrode 14 may also, on the otherhand, be relatively fast in that the concentration of associated metalcations in the electrolyte solution increases by about 0.1 weightpercent per battery power cycle. The leaching of any amount of metalcations from the positive electrode 14, whether slow or fast, cannevertheless poison large areas of the graphite in the negativeelectrode 12, and ultimately cause a noticeable andperformance-affecting reduction in capacity of the lithium ion battery10. An amount of chelating agents effective to sequester the cumulativedissolution of metal cations into the electrolyte solution during theoperational lifetime of the lithium ion battery 10 may therefore beattached to the microporous polymer separator 16 and/or the polymerbinding materials in at least one of the negative or positive electrodes12, 14. The exact amount of chelating agents employed, which may varyconsiderably, is generally predicated on the chemistry of the lithiumion battery 10, the compositional make-up of the negative and positiveelectrodes 12, 14, and the expected or observed rate at which unwantedmetal cations are introduced into the electrolyte solution duringoperation of the lithium ion battery.

The chelating agents may comprise, for example, at least one of a crownether, a podand, a lariat ether, a calixarene, a calixcrown, or mixturesthereof. These chelating agents are useful because they will notstrongly complex with the relatively small lithium ions moving betweenthe negative and positive electrodes 12, 14 because of their size andspatial constructions. Skilled artisans will generally know andunderstand, or be able identify, the many molecular compounds that mayconstitute these classes of chelating agents. A generalized descriptionof these chelating agents is nonetheless provided here for convenience.

A crown ether is a macrocyclic polyether in which the polyether ringincludes oxygen donor atoms that can complex with a metal cation. Someor all of the oxygen donor atoms in the polyether ring may be exchangedfor nitrogen atoms, a class of crown ethers known as azacrowns, orsulfur atoms, a class of crown ethers known as thiacrowns. The crownether may be monocyclic, in which the crown ether forms a somewhattwo-dimensional ring for complexing with a metal cation, or polycyclic,in which the crown ether forms a more three-dimensional cage forcomplexing with a metal cation. One example of a polycyclic crown etheris a cryptand. The crown ether may also be substituted at any locationalong its polyether ring by any of a variety of groups known to thoseskilled in the art. A podand is an acyclic polyether ligand thatincludes donor-group-bearing arms that can complex with a metal cation.A lariat ether is a crown ether that includes a donor-group-bearingside-arm that provides additional metal cation binding sites beyondthose present on the polyether ring. A calixarene is a metacyclophane ofmethylene-bridged phenol units, and is generally found in one of a cone,partial cone, 1,2-alternate, or 1,3-alternate conformation. A calixcrownis a calixarene that includes a polyether ring that links two phenolicoxygens of the calixarene framework. The indifference these chelatingagents show towards complexing with lithium ions is likely ascribed totheir relatively large polyether ring or cage structures and/or thespatial orientation of their functional donor-group-bearing arms whencompared to the relatively small size of lithium ions. Analogs andstructurally related molecules of the chelating agents just mentionedmay also be employed.

A nonexhaustive and exemplary list of crown ethers that can complex withmetal cations which may, for example, leach into the electrolytesolution from the positive electrode 14 (such as cations of manganese,cobalt, and iron) includes (1) 15-crown-5, (2) dibenzo-15-crown-5, (3)18-crown-6, (4) benzo-18-crown-6, (5) dibenzo-18-crown-6, (6)dibenzo-21-crown-7, (7) dicyclohexano-18-crown-6, (8)dicyclohexano-24-crown-8, (9) poly(dibenzo-18-crown-6), (10)1,4,7,10,13,16-hexathia-18-crown-6, (11)1,4,7,10,13,16-hexaaza-18-crown-6, (12) 1-aza-18-crown-6, (13)1,10-diaza-18-crown-6, (14) N,N′-dibenzyl-4,13-diaza-18-crown-6, and(15) 4,7,13,16,21,24-hexaoxa-1,10-diazabycyclo[9.8.8]hexacosane, thestructures of which are shown below. The hydrogen atoms in structures11-13 are assumed.

Some more examples of crown ethers, including thiacrowns and azacrows,that may be attached to the microporous polymer separator 16 can befound in W. Walkowiak and C. A. Kozlowski, “Macrocycle Carriers forSeparation of Metal Ions in Liquid Membrane Processes—A Review,”Desalination 240, Table 1 on pg. 189 (compounds 1-15 that are notalready mentioned above) (2009); R. L Bruening, R. M. Izatt, and J. S.Bradshaw, “Understanding Cation-Macrocycle Binding Selectivity inSingle-Solvent Extractions, and Liquid Membrane Systems by QuantifyingThermodynamic Interactions, FIG. 1 on pg. 112 in “Cation Binding byMacrocycles,” Y. Inoue and G. W. Gokel (editors), Chapter 2, 1990,Marcel Dekker Inc., New York and Basel; J. L. Tonor, “Modern Aspects ofHost-Guest Chemistry: Molecular Modeling and Conformationally RestrictedHosts,” FIG. 2 on pg. 82 in “Crown Ethers and Analogs,” S. Patai and Z.Rappaport (editors), Chapter 3, 1989, John Wiley and Sons, New York; F.Vögtle and E. Weber, “Crown-ether-complexes and Selectivity,” FIGS. 1,2, and 3 on pg. 209, 210, and 211, respectively, in “Crown Ethers andAnalogs,” S. Patai and Z. Rappaport (editors), Chapter 4, 1989, JohnWiley and Sons, New York.

A nonexhaustive and illustrative list of podands that can complex withmetal cations which may, for example, leach into the electrolytesolution from the positive electrode 14 can be found in W. Walkowiak andC. A. Kozlowski, “Macrocycle Carriers for Separation of Metal Ions inLiquid Membrane Processes—A Review,” Desalination 240, Table 2 on pg.190 (compounds 32a and 32b) (2009); A. Shahrisa and A. Banaei,“Chemistry of Pyrones, Part 3: New Podands of 4H-Pyran-4-ones, 5Molecules,” FIGS. 1 and 3 on pg. 201 (2000); and F. Vögtle and E. Weber,“Crown-ether-complexes and Selectivity,” FIGS. 4, 5, 6, and 7 on pg.212, 213, 214, and 215, respectively, in “Crown Ethers and Analogs,” S.Patai and Z. Rappaport (editors), Chapter 4, 1989, John Wiley and Sons,New York; and Crown Ethers and Analogs, edited by Patai and Rappoport,(1989.

A nonexhaustive and illustrative list of lariat ethers that can complexwith metal cations which may, for example, leach into the electrolytesolution from the positive electrode 14 can be found in W. Walkowiak andC. A. Kozlowski, “Macrocycle Carriers for Separation of Metal Ions inLiquid Membrane Processes—A Review,” Desalination 240, Table 1 on pg.189 (compounds 16-18) (2009); and E. Weber, “New Developments in CrownEther Chemistry: Lariats, Spherands, and Second-Sphere Complexes,” FIGS.2, 4, and 6 on pg. 307, 309, and 315, respectively, in “Crown Ethers andAnalogs,” S. Patai and Z. Rappaport (editors), Chapter 5, 1989, JohnWiley and Sons, New York.

A nonexhaustive and illustrative list of calixarenes that can complexwith metal cations which may, for example, leach into the electrolytesolution from the positive electrode 14 can be found in W. Walkowiak andC. A. Kozlowski, “Macrocycle Carriers for Separation of Metal Ions inLiquid Membrane Processes—A Review,” Desalination 240, Table 2 on pg.190 (compounds 22-23) (2009); and J. L. Atwood, “Cation Complexation byCalixarenes,” FIGS. 6 and 7 on pg. 587 (the ester functionalizedcalixarenes) in “Cation Binding by Macrocycles,” Y. Inoue and G. W.Gokel (editors), Chapter 15, 1990, Marcel Dekker Inc., New York andBasel.

A nonexhaustive and illustrative list of calixcrowns that can complexwith metal cations which may, for example, leach into the electrolytesolution from the positive electrode 14 can be found in W. Walkowiak andC. A. Kozlowski, “Macrocycle Carriers for Separation of Metal Ions inLiquid Membrane Processes—A Review,” Desalination 240, Table 2 on pg.190 (compounds 24-27, compound 28 with ester functionality, andcompounds 30-31) (2009.

There are, of course, many other crown ethers, podands, lariat ethers,calixarenes, calixcrowns, and related chelating agents that are known toskilled artisans, but are not specifically mentioned here, that can beattached to the microporous polymer separator 16 to sequester andimmobilize unwanted metal cations that may be introduced into theelectrolyte solution of the lithium ion battery 10.

The chelating agents may be attached to the microporous separator 16,the negative and positive electrodes 12, 14, or the battery component byany of a variety of methods. For example, in one embodiment, a pendantgroup that comprises the chelating agent may be grafted onto thepolyolefin used to make the microporous polymer separator 16. Thechelating agents may be attached uniformly throughout polyolefin or theymay be locally attached at predetermined locations. A greaterconcentration of the chelating agents may, for example, be provided onthe side of the microporous polymer separator 16 that faces the positiveelectrode 14. Such a build-up of chelating agents on thepositive-electrode-side of the microporous polymer separator 16 can helpfacilitate the earliest possible sequestering of any destructive metalcations that leach into the electrolyte solution from the positiveelectrode 14. Pendent groups that comprise the chelating agents may alsobe similarly grafted onto the other polymers in the microporous polymerseparator 16, if present. In another embodiment, an insoluble polymerbound group that comprises the chelating agent may be entangled in, andoptionally crosslinked to, the polymer matrix of the microporousseparator 16 and/or the polymer binder materials of at least one of thenegative or positive electrodes 12, 14. The polymer bound group may bepolyolefin, or some other polymer with similar properties, that includesa pendent group that comprises the chelating agent.

A poly(1-olefin) may be prepared, for instance, from the Ziegler-Nattapolymerization of functionally substituted polyolefins or by metathesispolymerization. The resultant poly(1-olefins) may then be functionalizedwith the chelating agents. The same chelating agent substitutedpolyolefins may also be prepared by the polymerization of α,ω-olefins orpre-formed prepolymers that have been substituted with pendant chelatingagent groups. Polyolefin heteropolymers, such as polyundecylenol, may beformed by either method and generally involve the controlled feed ofsimilarly sized (i.e., number of carbons) olefin monomers or prepolymersduring polymerization. The chelating agent substituted polyolefins, onceprepared, may then be incorporated into the microporous polymerseparator 16. In one embodiment, the chelating agent substitutedpolyolefins may be manufactured into a fairly rigid fibrous polyolefinlayer that may constitute all or part of the microporous polymerseparator 16. In another embodiment, however, the chelating agentsubstituted polyolefins may be insolubly bound within the polymer matrixof a separate fibrous polymer layer that is intended for use as all orpart of the microporous polymer separator 16, or they may be insolublybound within the polymer matrix of a polymer binder materials that isintended to be included in at least one of the negative or positiveelectrodes 12, 14.

The following examples are provided to help illustrate how a chelatingagent substituted polyolefin may be prepared, and how such polyolefinsmay be incorporated into the microporous polymer separator 16 and/or thepolymer binder materials of at least one of the negative or positiveelectrodes 12, 14. Example 1 demonstrates the preparation of apolyolefin that includes pendent crown ether groups in which afunctionally substituted polyolefin was polymerized and then substitutedwith crown ether groups. Example 2 demonstrates the preparation of apolyolefin that includes pendent crown ether groups in which olefinswere substituted with crown ether groups and then polymerized. Example 3demonstrates the manufacture of a microporous polymer separator from thepolyolefins of either Example 1 or Example 2. The microporous polymerseparator manufactured in Example 3 includes a polyolefin layer havingpendent crown ether groups. Example 4 demonstrates the manufacture of amicroporous polymer separator or a negative electrode. In that Example,crown ether substituted polyolefins are insolubly bound within thepolymer matrix of a commercially available polyolefin battery separatoror a commercially available polymer binder material. Those materials maythen be incorporated into a microporous polymer separator or a negativeelectrode, respectively.

Example 1

In this example, a polyolefin with pendent 18-crown-6 groups (crownether chelating agent) is prepared by the Zeigler-Natta polymerizationof a halogenated polyolefin that is subsequently substituted withfunctionalized crown ether groups. The halogenated polyolefins may beformed by the direct polymerization of halo-functionalized monomers orthe chemical modification of pre-formed prepolymers. To accomplish this,at least one α,ω-olefin such as 11-undecylenyl bromide (or iodide),6-bromo-1-hexene, or 5-bromo-1-pentene may be polymerized with at leastone 1-olefin such as ethane, propene, or 1-butene at a prefixedα,ω-olefin:1-olefin weight ratio of, for example, 1:9, 2:8, 3:7, or 5:5in toluene. A catalyst, such as TiCl₃.AA/Et₂AlCl, may be used to makeisotactic poly-α-olefins that form α-helix structures and polymerize theω-substituted α-olefins. This polymerization reaction proceeds mostefficiently when bulky monomer or prepolymer functionalized units thatdo not coordinate with the catalyst are used [e.g. CH₂═CH—(CH₂)_(y)—X].Large halo groups (X) may also enhance the polymerization reaction(i.e., I>Br>Cl). The resultant polymers, which are soluble in hottoluene, can form carboxylic acid and alcohol functional groups byprotection with, for example, trimethylsilyl-groups [—Si(CH₃)₃], whichare readily removed on work-up with aqueous acids. Nucleophilicdisplacement of the halide ion with 2-hydroxymethyl-18-crown-6,hydroxymethyl-benzo-18-crown-6, or 2-aminobenzo-18-crown-6 in thepresence of potassium carbonate and/or lutidine may then be achieved toattach pendent groups containing 18-crown-6 to the polyolefins.Moreover, at high concentrations of crown ether substituent groups, thepolyolefins become less crystalline and may therefore be reinforced with1,6-hexadience as a co-reactant to cross-link the polyolefins. Theoverall reaction in which pendent 18-crown-6 groups are grafted onto apolyolefin is shown below, where X may be I or Br, and Y may be2-hydroxymethyl, hydroxymethyl-benzo, or 2-aminobenzo.

Example 2

In this example, a polyolefin with pendent 18-crown-6 groups (crownether chelating agent) is prepared by polymerizing α,ω-olefins orpre-formed prepolymers that have first been substituted with pendantcrown ether groups. Crown ether substituted α,ω-olefins may be preparedby reacting at least one of 11-undecylenyl bromide (or iodide),6-bromo-1-hexene, or 5-bromo-1-pentene with at least one ofhydroxymethyl-18-crown-6 or hydroxymethyl-benzo-18-crown-6 inN,N-dimethylacetamide. Alcohol functional groups may be formed on theα,ω-olefins by protection with, for example, trimethylsilyl-groups[—Si(CH₃)₃], which are readily removed on work-up with aqueous acids.Nucleophilic displacement of the halide ion with2-hydroxymethyl-18-crown-6 or hydroxymethyl-benzo-18-crown-6 in thepresence of potassium carbonate and/or lutidine may then proceed untilthe bromo (or iodo) groups on the α,ω-olefins are replaced with18-crown-6 groups. The crown ether substituted α,ω-olefins are thenpolymerized with at least one 1-olefin such as ethane, propene, or1-butene at a pre-fixed α,ω-olefin:1-olefin weight ratio of, forexample, 1:9, 2:8, 3:7, or 5:5 in toluene. A catalyst, such asTiCl₃.AA/Et₂AlCl, may be used to make isotactic poly-α-olefins that formα-helix structures and polymerize the ω-substituted α-olefins. Moreover,at high concentrations of crown ether substituent groups, thepolyolefins become less crystalline and may therefore be reinforced with1,6-hexadience as a co-reactant to cross-link the polyolefin. Theoverall reaction in which pendent 18-crown-6 groups are grafted onto apolyolefin is shown below, where X may be I or Br, and Y may be2-hydroxymethyl, hydroxymethyl-benzo, or 2-aminobenzo.

In a typical reaction, 6-bromo-1-hexene is allowed to react with a onemolar ratio of hydroxymethyl-benzo-18-crown-6 in N,N-dimethylacetamidefor 1 week at 50° C. under argon in a sealed vessel in the presence ofexcess potassium carbonate and a molecular equivalent of lutidine. Thereaction mixture is filtered and the solvent and lutidine are thenremoved under vacuum and 1-hexyl-6-benzo-18-crown-6 is purified onsilica gel by column chromatography eluting with tetrahydrofuran,methylene chloride, or ethyl acetate and hexanes. After removal of thesolvent, the residue is dissolved in 10 wt. % toluene, 1 wt. %1,6-hexadiene, and with 89 wt. % 1-butene bubbled into a glass beveragebottle with a rubber septum that is situated in an ice bath. Thereactants in toluene are double-needle, dropwise transferred intoanother beverage bottle with a rubber septum under argon, situated in anice bath, and containing a magnetic stir bar, toluene, TiCl₃.AA, 25 wt.% diethylaluminum chloride in toluene, and optionally a 1.1 molarsolution of diethyl zinc, all of which are added to methanol using aWaring blender to fibrillate the precipitated crown ether substitutedpolyolefin as a fibrous pulp.

Other Examples

A more complete discussion of various techniques that can be used tograft crown ethers onto polymer backbones can be found in J. Smid, PureAppl. Chem., 48, 343 (1976), J. Smid, Makrom. Chem. Supp., 5, 203(1981), J. Smid, Pure Appl. Chem., 54, 2129 (1982), and U. Tunca and Y.Yagci, “Crown Ether Containing Polymers,” Prog. Polym. Sci., 19, 233-286(1994). Another method of making poly(olefins) with pendent crown ethersis to prepare poly(vinyl benzyl alcohol) containing polymers, asdiscussed in U.S. Pat. No. 6,200,716 to Fuller, and then react thosepolymers with chloromethyl-benzo-18-crown-6 in N,N-dimethylacetamide.Still another method involves preparing olefinic polymers withundecylenyl alcohol groups and allowing those polymers to react withlithium hydride in tetrahydrofuran in the presence ofchloromethyl-benzo-18-crown-6.

Example 3

The crown ether substituted polyolefins prepared by the method of eitherExample 1 or Example 2 may be added to a non-solvent such as methanol toform insoluble flocculated fibrous materials (flocs). The crown ethersubstituted polyolefins may, alternatively, be quenched with methanol,washed with water, and then stripped of toluene under reduced pressure.The polyolefins may then be fibrillated in a non-solvent such as waterusing a Waring blender. Next, the fibrillated polyolefins may be pouredonto and laid down on a porous screen. The wet pulp polyolefin materialmay then be pressed to remove any residual non-solvent to form a fibrousmat, and subsequently hot pressed below the melting point of thepolyolefin to form a fairly rigid crown ether substituted fibrouspolyolefin material layer. The resultant polymer layer may then beutilized in a lithium ion battery as either a single layer microporouspolymer separator or as part of a multi-layer microporous polymerseparator.

Example 4

The crown ether substituted olefins (vinyl benzo-18-crown-6) prepared bythe method described by J. Smid (see OTHER EXAMPLES above), or purchasedfrom Aldrich of Milwaukee, Wis., may be dissolved in a toluene orbenzene solution that optionally, but preferably, includes across-linking agent such as divinylbenzene with azobisisobutyronitrile(0.1 wt. % monomer mass). A commercial polyolefin lithium ion batteryseparator or a commercially available binder material may be dipped intothe solution with subsequent heating under nitrogen between 60° C. and80° C. so that polymerization of the crown ether substituted olefins canoccur in the presence of the separator or polymer binder material.Commercial polyolefin battery separators, either single ormulti-layered, are available from Asahi Kasei, headquartered in Tokyo,Japan, Celgard LLC, headquartered in Charlotte, N.C., Ube Industries,headquartered in Tokyo, Japan, and Mitsui Chemicals, headquartered inTokyo, Japan, to name but a few manufacturers. The dissolved crown ethersubstituted polyolefins, at this point, become snagged in the polymermatrix of the commercial battery separator or the commercially availablepolymer binder material. Later, when the commercial battery separator orthe commercially available polymer binder material is removed from thesolution and air dried, the entrapped crown ether substitutedpolyolefins become insoluble polymer bound polyolefin particles. Thepresence of a cross-linker can enhance the entanglement of the crownether substituted polyolefins contained in the commercial batteryseparator or the commercially available polymer binder material bypromoting the formation of stronger polymer-polymer bonds between thepolymer bound crown ether substituted polyolefins and between thepolymer bound crown ether substituted polyolefins and the commercialbattery separator/commercial polymer binder materials.

Additives (such as crown ethers, aza-crowns, thia-crowns, cryptands,etc.) are grafted or bonded onto, or otherwise attached the ceramicpowders or materials that are part of the separator, or are includedinto or coated onto the electrodes or other battery components, so thatthe trapped cations cannot reach the negative electrode, since thechelating structures are tethered to ceramic materials that areimmobilized inside the battery. Seven possible embodiments of theinvention (for functionalizing silicas and alumina) are as follows: (1)(EtO)3SiCH2CH2CH2-NH2+chioromethylbenzo-18-crown-6 followed byhydrolysis of the crown ether functionalized silane; (2)(EtO)3SiH+CH2=CH(CH2)8CH2O—CH12-18-Crown-6+Pt catalyst followed byhydrolysis of the crown ether functionalized silane; (3)3-glycidoxypropyltri(ethoxy)silane+HOCH2-18-crown-6 followed byhydrolysis of the crown ether functionalized silane; (4)2-chloroethyltriethoxysilane+HOCH2-18-crown-6 followed by hydrolysis ofthe crown ether functionalized silane; (5)methacryloxypropyltris(methoxy)silane+vinyl benzo-18-crown-6 followed,by hydrolysis of the crown ether functionalized silane; (6)7-octenyltrimethoxysilane (or10-undecenyltrimethoxysilane)+undecylenyl-hydroxy-methyl-18-crown-6,followed by hydrolysis of the crown ether functionalized silane; (7)(EtO)3SiCH2CH2CH2-SH+chioromethylbenzo-18-crown-6 followed by hydrolysisof the crown ether; this can also be functionalized with alumina.

The above description of embodiments is merely illustrative in natureand, thus, variations thereof are not to be regarded as a departure fromthe spirit and scope of the invention.

What is claimed is:
 1. A method comprising: attaching one or morechelating agents to a lithium ion battery component, the one or morechelating agents being constructed and arranged to complex with metalcations but not strongly complex with lithium ions.
 2. The method ofclaim 1, wherein the one or more chelating agents comprise at least oneof a crown ether, a podand, a lariat ether, a calixarene, a calixcrown,a crytand or a mixture of two or more of these chelating agents.
 3. Themethod of claim 1, wherein the metal cations comprise at least one ofMn²⁺, Co²⁺, Ni²⁺ or Fe²⁺.
 4. The method of claim 1, comprising amicroporous separator comprising a polymer material or ceramic materialhaving the chelating agent bound or attached thereto.
 5. The method ofclaim 4, wherein the polymer material comprises a polyolefin comprisingpendent groups that comprise the one or more chelating agents.
 6. Themethod of claim 4, comprising an electrode comprising a polymer materialor ceramic material having one or more chelating agents attached orbound thereto.
 7. The method of claim 4, wherein the component is not aseparator or electrode.
 8. The method of claim 4, wherein the componentcomprises at least one of a silica or alumina.
 9. The method of claim 1,wherein the battery component comprises at least one of a negativeelectrode, a positive electrode, or a microporous separator positionedbetween the positive electrode and negative electrode.
 10. The method ofclaim 9, the battery component comprises at least one of a polymermaterial or a ceramic material.
 11. The method of claim 1, wherein thechelating agents comprise at least one of a crown ether, a podand, alariat ether, a calixarene, a calixcrown, a crytand or a mixture of twoor more of these chelating agents, and wherein the chelating agents areattached to at least one of the polymer material or ceramic material.12. A method as set forth in claim 1 wherein the attaching comprises areaction with a crown ether.
 13. A method as set forth in claim 12wherein the crown ether includes 18-crown-6.
 14. A method as set forthin claim 12 wherein crown ether is monocyclic.
 15. A method as set forthin claim 12 wherein the crown ether includes a two-dimensional ring. 16.A method as set forth in claim 12 wherein the crown ether includes athree-dimensional ring.
 17. A method as set forth in claim 12 whereinthe reaction produces a crown ether functionalized silane.
 18. A methodas set forth in claim 12 wherein the reaction produces a crown etherfunctionalized alumina.
 19. A method as set forth in claim 12 whereinthe reaction produces a crown ether functionalized polymer.
 20. A methodas set forth in claim 12 wherein the reaction produces a 18-crown-6functionalized silane, alumina or polymer.
 21. A method as set forth inclaim 13 wherein the attaching comprises the reaction of(EtO)3SiCH2CH2CH2-NH2+chioromethylbenzo-18-crown-6 followed byhydrolysis of the crown ether functionalized silane.
 22. A method as setforth in claim 13 wherein the attaching comprises the reaction of(EtO)3SiH+CH2=CH(CH2) 8CH2O—CH12-18-Crown-6+Pt catalyst followed byhydrolysis of the crown ether functionalized silane.
 23. A method as setforth in claim 13 wherein the attaching comprises the reaction of3-glycidoxypropyltri(ethoxy)silane+HOCH2-18-crown-6 followed byhydrolysis of the crown ether functionalized silane.
 24. A method as setforth in claim 13 wherein the attaching comprises the reaction of2-chloroethyltriethoxysilane+HOCH2-18-crown-6 followed by hydrolysis ofthe crown ether functionalized silane.
 25. A method as set forth inclaim 13 wherein the attaching comprises the reaction ofmethacryloxypropyltris(methoxy)silane+vinyl benzo-18-crown-6 followed byhydrolysis of the crown ether functionalized silane.
 26. A method as setforth in claim 13 wherein the attaching comprises the reaction of7-octenyltrimethoxysilane (or10-undecenyltrimethoxysilane)+undecylenyl-hydroxy-methyl-18-crown-6,followed by hydrolysis of the crown ether functionalized silane.
 27. Amethod as set forth in claim 13 wherein the attaching comprises thereaction of (EtO)3SiCH2CH2CH2-SH+chioromethylbenzo-18-crown-6 followedby hydrolysis of the crown ether; this can also be functionalized withalumina.